if these are the regular galaxy buds. in the galaxy wearable app. go to about earbuds-> reset earbuds. you will need to keep the case open while they reset. they should reconnect after.
maybe there is dirt in it. if you have a spare toothbrush, you can try to use that to clean it out. or if you have a can of air. if not you can try and use the seeing under accessibility->hearing enhancements->left/ right sound balance. this will shift the balance from one earbud to the other. or maybe mono sounds may help if you try that first.